[Asterisk-Users] Maximum tollerable lag/jitter for IAX2 w/o jitterbuffer enabled?

[Benjamin on Asterisk Mailing Lists]

On Tue, 7 Sep 2004 16:26:24 -0700, Kris Boutilier
<kris.boutilier at scrd.bc.ca> wrote:
>  I'm having a problem with intersite calls over IAX2 being abruptly
> terminated. Nothing odd shows in any of the logs for Asterisk or the host.
> The only think I can think it might be is a lag-spike on the site to site
> connection.

When does the cut off occurr? Is it always after about 8-10 seconds?
If so, you may have a problem with IAX transfer. You can verify this
by using notransfer=yes.


>  How sensitive is IAX2 to lost frames, lag spikes or large variations in
> jitter with the GSM codec <snip>
> 
> During an average call 'iax2 show channels'
> provides:
> 
> Peer             Username    ID (Lo/Rem)  Seq (Tx/Rx)  Lag      Jitter
> JitBuf  Format
> 10.0.40.140      astpbx-woo  00002/00002  00005/00006  00040ms  0036ms
> 0000ms  GSM

Those values are certainly no problem for IAX at all. I have made hour
long IAX calls with both lag and jitter often going well above 1
second and the calls never terminated. All you get is a heavy delay on
the audio and occasional drop outs, but you shouldn't get cut off.

Even if the lag goes above 2 seconds and you have qualify=yes, the
calls will not normally be cut off when Asterisk reports "peer now to
lagged". As long as the lag will go back below 2 seconds within a
reasonable time frame the connection will recover. IAX is extremely
robust, it is rare to have a connection terminate due to network
problems.

rgds
benjk
-- 
Sunrise Telephone Systems, 9F Shibuya Daikyo Bldg., 1-13-5 Shibuya,
Tokyo, Japan.

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